I do just the opposite, I write until I don't know. Things jumble around in my brain until, at odd moments, I see a piece of a story - often contained in a single phrase - such as:

"You always knew?" the boy asked the man.

I write furiously until that scene is recorded and there is no more. If I force it further, I bore myself.

When do I write? Late at night when the house is quiet and my children asleep. The hours until midnight are deliciously my own.

It is important for me to capture ideas in the instant; I call it my notebook habit. I can feel the ideas there, like wisps; if I do not write them down, they fade as if they never were. I cannot get them back.